Today, a lot of vessels are equipped with a technology called Automatic Identification System (AIS) that periodically broadcasts or announces certain information about each vessel using select radio frequencies. The use of AIS is mandated under the United Nations SOLAS convention for all international vessels over 300 tons, cargo vessels over 500 tons and passenger ships of all sizes. Coastal authorities rely on the AIS information to coordinate, manage and track maritime traffic near the coast. The AIS information is vital to ensuring a vessel's safe and legal path through the ocean, and in the prevention of accidents, piracy, illegal fishing, and human trafficking, among other illicit activities.
Typically, an AIS transponder is installed on a vessel and programmed to automatically broadcast a message, such as a beacon, containing data including the vessel's identity, speed, heading and navigational status, on a periodic basis such as every 2-10 seconds. The AIS transponder broadcasts the message in certain predefined radio frequency channels, including for example, AIS 1 (161.9625-161.9875 MHz) and AIS 2 (162.0125-162.0375 MHz), among others.
However, not all vessels are equipped with AIS. Sometimes, vessels that are equipped with AIS would deliberately disable broadcasting AIS beacons. For example, a vessel that does not wish its action to be known can circumvent the AIS by powering down the AIS or disabling its AIS beacon. Once the AIS is powered off, the vessel becomes a “dark target” or goes off-the-grid. In another example, a vessel may also spoof its AIS by modifying the information sent to reflect an incorrect name, location, speed, or bearing. Without revealing its true information, vessels may engage in illegal activities. Such illegal activities create serious problems for law enforcement, insurance agencies, governments and shipping companies, among others. In addition, a faulty or non functioning AIS can be a safety hazard.
Therefore, there is a need for a mechanism to track vessels in the absence of correct AIS data.